A broad survey of the experimental database of neutral beam heated plasmas in the JET tokamak has established the theoretically expected ubiquity, in rotating plasmas, of a convective transport mechanism which has its origin in the vertical particle drift resulting from the Coriolis force. This inward convection, or pinch, leads to inward transport of toroidal angular momentum and is characterized by pinch numbers RV/chi(phi), which rise from near unity at r/a approximate to 0.25 to around 5 at r/a approximate to 0.85. Linear gyrokinetic calculations of the Coriolis pinch number and the Prandtl number chi(phi)/chi(i) are in good agreement with the experimental observations, with similar dependences on plasma parameters. The data, however, do not rule out contributions from different processes, such as residual stresses.